Compound (A) is a compound represented by the following formula:

Compound (A) or a salt thereof has been reported as an inhibitor of dipeptidyl peptidase (DPP-IV), which is an enzyme that decomposes glucagon-like peptide-1 (GLP-1), a hormone increasing insulin secretion (patent document 1).
In addition, a method including administering 1-250 mg of compound (A) or a salt thereof to a patient once per week (patent documents 2, 3), crystal polymorphs of compound (A) (patent documents 4, 5), and a preparation of compound (A) (patent documents 6, 7) have also been reported. Compound (A) and a salt thereof are recommended for oral administration in view of the easiness of self-administration, and a tablet, particularly a tablet in the dosage form for administration once per week, is desired.
The dosage form of once per week is expected to improve drug compliance of patients, whereas it requires supply of compound (A) or a salt thereof to patients in a high dose as compared to, for example, the dosage form of once per day. Since a solid preparation containing compound (A) or a salt thereof in a high dose increases its size, it may conversely degrade the drug compliance for patients, particularly infants and elderly patients having difficulty in swallowing.